1. Field of the Invention
The present invention relates to a hemming process and a hemming apparatus, which hems a panel on a lower mold while actuating an upper mold in a vertical direction.
2. Description of the Prior Art
A door panel for a vehicle or a similar panel is formed by putting an inner panel together with an outer panel (the state of these panels being together with each other is referred to as a xe2x80x9cmarriage panelxe2x80x9d), and hemming the marriage panel as a rule. The hemming process is a process in which an edge portion of one panel is rolled up, to be unified with the other panel which is in a clamped state.
With reference to the attached drawings, the conventional hemming apparatus used in such a hemming processing and the conventional hemming process utilizing the same will now be described.
FIG. 8 is an explanatory view showing the conventional hemming apparatus, where FIG. 8A is a perspective view of one example of the conventional hemming apparatus (hereinafter referred to as the xe2x80x9cfirst conventional apparatusxe2x80x9d), and FIG. 8B is a perspective view of another example of the conventional hemming apparatus (hereinafter referred to as the xe2x80x9csecond conventional apparatusxe2x80x9d).
The first conventional apparatus 100 and the second conventional apparatus 200 have upper molds 101, and 201, lower molds 102 and 202, respectively. In each case, the lower mold 102 or 202 is fixed at the position to be hemmed, and the upper mold 101 or 201, which is actuated vertically, is placed upside the lower mold 102 or 202.
In the first conventional apparatus 100, a part of the lower mold 102 is cut out and an insert hole 103 is formed at this position, into which a means 104 for material handling with a marriage panel W is inserted.
An outer panel W1 and an inner panel W2 are unified with each other to form the marriage panel W, and the marriage panel thus formed is set onto the means 104 of material handling. The means 104 of material handling, onto which the marriage panel W is set, is transported by a robot arm 105 to be inserted into the insert hole 103. Upon inserting the means 104 of material handling at a prescribed position, the upper mold 101 descends to thereby apply the marriage panel W to hemming processing.
In the case of the second conventional apparatus 200, no insert hole is formed in the lower mold 202. Instead of the insert hole 102, a stroke length ST of the vertical movement of the upper mold 202 takes long, and the marriage panel W is directly set onto the lower mold 202.
More specifically, first a sufficient distance is formed between the upper mold 201 and the lower mold 202 by the vertical movement of the upper mold 201. Thereafter, the robot arm 205 adsorbs and holds the marriage panel W, and the marriage panel W is set at a prescribed position of the lower mold 202 by means of the bending movement of the robot arm 205. After the marriage panel W has been set, the robot arm 205 leaves the marriage panel W, and then the upper mold 201 descends to press the marriage panel W to carry out hemming processing.
In the case of the first conventional apparatus 100, since the marriage panel is set by inserting the means of material handling into the insert hole 103, the hemming processing at the edge of the marriage panel W position near the insert hole 103 cannot be applied. Specifically, if the marriage panel W should be applied to the hemming processing over the entire circumferences of the marriage panel W, the first conventional apparatus 100 cannot be applied.
On the other hand, according to the second conventional apparatus, it is possible to apply the hemming processing over the entire circumferences of the marriage panel W. However, in the case of the second conventional apparatus, since it is necessary to take a large length of the vertical stroke ST of the upper mold 201, the apparatus 200 itself becomes large. In particular, since the upper mold 201 has a heavy weight, the apparatus must have a construction which can bear such a heavy weight. Moreover, if a sufficient stroke length ST of the vertical movement of the upper mold 202 is secured, the cost for producing the apparatus is increased, resulting in higher production costs.
Furthermore, a stroke length ST of the vertical movement of the upper mold 202 lead to a long processing cycle time, delaying the processing time and lowering the process efficiency.
An object of the present invention is to solve the problems associated with the prior art and to provide a hemming process and a hemming apparatus which can reduce the cycle time to enhance the workability.
According to the present invention, a hemming process comprises putting one panel together with another panel to form a marriage panel, and unifying these panels with each other by clamping the marriage panel between an upper mold and a lower mold; said process involving the following steps:
a first step for setting said marriage panel onto the lower mold by a transporting unit;
a second step for moving the lower mold on which said marriage panel has been set to the position to be hemmed, facing to upper mold by means of a mechanism for moving the lower mold; and
a third step for vertically moving the upper mold to the position corresponding to the lower mold moved to the position to be hemmed to thereby compress the marriage panel.
In order to put this process into practical utilization, there is provided a hemming apparatus for vertically moving an upper mold toward a lower mold to thereby compress said marriage panel whereby the marriage panel is hemmed; said apparatus further comprising:
a mechanism for moving the lower mold in the horizontal direction to allow the lower mold to be movable from the position to be hemmed facing to the upper mold and a position for setting the panel where said marriage panel is set.
According to the hemming process and the hemming apparatus according to the present invention, the hemming cycle time can be reduced.
According to the preferred embodiment of the hemming apparatus of the present invention, the hemming apparatus is equipped with a mechanism for floating the lower mold which supports the lower mold in a floating state.
In this preferred embodiment, since it is not necessary to lift the lower mold for every movement of the lower shift by means of a die lifter or such, the time required for moving the lower mold can be reduced.